This invention relates in general to a process for fabricating drum and end flange assembly and apparatus for carrying out the process, more specifically, to a process and apparatus for adhesively securing a drum to an end flange.
A photoreceptor conventionally utilized for copiers and printers comprises a hollow electrically conductive metal drum substrate which has been dip coated with various coatings including at least one photoconductive coating comprising pigment particles dispersed in a film-forming binder. These drum type photoreceptors are usually supported on an electrically conductive shaft by drum supporting end flanges (hubs). The hubs are usually constructed of plastic material and have a hole through their center into which a supporting axle shaft is inserted. Generally, at least one of the hubs carries a gear that is either molded in place during formation of the hub or fastened to the hub after the hub is formed. This gear is driven by a powered gear to rotate the drum during image cycling. Since the hubs are usually constructed of electrically insulating plastic material, a suitable electrical grounding means such as a flexible spring metal strip is secured to the hub and positioned to contact both the electrically conductive axle shaft and the electrically conductive metal substrate of the photoreceptor drum to ensure grounding of the drum through the shaft. Various types of grounding means are illustrated in U.S. Pat. No. 4,561,763 and U.S. Pat. No. 5,357,321, the entire disclosures thereof being incorporated herein by reference.
Often the hub or end flange is secured to the end of the drum by a thermoplastic or thermosetting resin adhesive. The use of an adhesive requires a number of manipulation steps and complex equipment to mount a hub to the end of a hollow drum. Solvents may be utilized to apply an adhesive solution to the inside edge of one end of a drum prior to mounting of the hub to the end of the drum. However, safety equipment is required such as solvent recovery systems including large hoods, condensers and other expensive and space consuming equipment to capture the solvent vapors emitted by the adhesive solution during drying. Further, if an adhesive applicator fails to apply an adhesive to the inside edge of one end of a drum, the hub will either fall out after mounting or slip during image cycling. A vision system such as a video camera may be utilized to ensure that the adhesive has, in fact, been applied. However, many adhesives are transparent and difficult to detect visually. A fluorescent tracer material can be added to the adhesive to render it more visible to the video camera. Unfortunately, most solvent adhesives exhibit poor holding strength and can have a short pot life. A short pot live can cause solidification and clogging in the equipment thereby requiring time consuming efforts to clean and remove the solidified adhesive. Failure of hubs to be adhesively secured to a drum ultimately leads to unacceptable copy output. Poor adhesive holding strength and the need for solvent recovery systems can be avoided by replacing solvent adhesives with a solvent free two part epoxy adhesive system. However, a two part epoxy adhesive system comprising a resin (usually about 50 percent by volume) and a curing agent, such as a hardener, (usually about 50 percent by volume) can present a product quality problem in situations where the adhesive appears to have been properly applied to the inside edge of one end of a drum prior to mounting of the hub when, in fact, only the resin or only the curing agent, rather than both, was applied. When only one of the two critical components of an epoxy adhesive has been applied to the inside edge of one end of a drum, the deposited material cannot form a cured epoxy resin adhesive and subsequent installation of the hub into the drum will result in the hub falling out of the end of the drum during packaging or during installation in customer replacement units, or cause the hub to slip in the drum during image cycling in an electrostatographic copier, duplicator or printer. The addition of a fluorescent tracer to either the resin component or the curing agent component of an epoxy resin adhesive facilitates detection of the presence on the inside edge of the drum of only the component containing the fluorescent tracer material. Unfortunately, detection of the presence of only one of the two critical epoxy adhesive components on the inside edge of one end of a drum, does not guarantee that the other component is also present and, therefore, does not solve the problem where the hub falls out of the end of the drum during further processing, during installation in customer replacement units, or failure of the drum-hub assembly to function properly in an electrostatographic copier, duplicator or printer.
Thus, there is a continuing need for improved electrostatographic imaging drum systems in which end flanges are more reliably secured to the drum.